Plants of Rhodiola L. of Crassulaceae are perennial herbaceous or subshrub plants. There are about 90 species of such plants in the world, in which 73 species exist in China. For the study of various plants of Rhodiola L., domestic and foreign scholars mainly focus on more than ten species such as Rhodiola crenulata, Rhodiola rosea, Rhodiola dumulosa, Rhodiola sachalinensis, Rhodiola kirilowii and Rhodiola sacra. Various species of Rhodiola L. have great difference in chemical compositions and efficacy. The plant of Rhodiola L. recorded in Chinese Pharmacopoeia (Edition 2015) refers to the dry radix and rhizome of Rhodiola crenulata, a plant of Crassulaceae which is featured by sweet and bitter taste. It can affect the lung meridian and the heart meridian, and has the effects of benefiting qi for activating blood circulation, dredging arteries and relieving asthma for diseases with qi deficiency and blood stasis, chest stuffiness and pains, hemiplegia and listlessness and asthma. Due to its anti-fatigue effect superior to ginseng and acanthopanax root, and its exciting intellectual activity efficacy superior to acanthopanax root, it is often taken as a good nutrition medicine by people to eliminate fatigue and withstand coldness.
Modern medicine indicates that the main effective components of Rhodiola L. are flavonoids, tyrosol and its glycosides. The flavonoids mainly include herbacetin and its corresponding glycosides. Herbacetin can effectively eliminate DPPH free radicals and hydroxyl radicals and inhibit protein oxidation, and its antioxidant activity is stronger than other glycosides. Researches show that the pharmacological activity decreases after the glycosylation of the 7th hydroxyl group of ring A in the structure of herbacetin. The more sugar content exists, the lower the activity is. The antioxidant activity of flavonoids compounds increases with the phenolic hydroxyl groups in the molecule. In addition, herbacetin can induce the apoptosis of human hepatocellular carcinoma cell HepG2 and has a potential to be developed into a new anti-cancer preparation.
Herbacetin refers to 3,4′,5,7,8-pentahydroxyflavone, which mainly exists in the plants of Crassulaceae. Researches indicate that Rhodiola L. has very low content of free herbacetin. Upon analysis on 12 different sources of medical Rhodiola L. (including the control Rhodiola crenulata with batch No. 121412-200902 and Rhodiola sachalinensis with batch No. 121657-201101 provided by National Institutes for Food and Drug Control, NIFDC)), it is found that the content of free herbacetin in them is only 0.0022%-0.061%. See Table 1 for specific data.
TABLE 1Free herbacetin content in rhodiola rosea from 12 different sourcesSample No.SourceHerbacetin content 1Nyingchi Prefecture in0.00416%Tibet Autonomous Region 2Shannan prefecture in0.00496%Tibet Autonomous Region 3Lijiang Houshan Area of0.00432%Yunnan 4Changbai Mountain of0.00232%Jilin 5Tibet No. 10.00710% 6Tibet No. 2 0.0129% 7Tibet No. 3 0.0109% 8Tibet No. 40.00580% 9Tibet No. 5 0.0607%10Tibet No. 60.00699%11Rhodiola crenulata from 0.0223%NIFDC12Rhodiola sachalinensis0.00409%from NIFDC
The process for direct separation of free herbacetin from medical Rhodiola L. has high difficulty and low yield, and it is not suitable for industrial production and is difficult to meet the needs of scientific research and new drug research and development, thus seriously limiting its in-depth research. However, the content of glycosides (e.g., herbacetin-7-0-rhamnoside and herbacetin-7-0-(3″-β-D-glucosyl)-rhamnoside) with herbacetin as aglycone is relatively high in the plants of Rhodiola L.
At present, few research reports on herbacetin are available, and no process route is disclosed so far suitable for the industrial production and preparation of high-purity herbacetin.